The present invention relates to a method for producing a peptide preparation that is both glutamine-rich and gluten-free and to the preparation thus obtained. The invention also relates to the use of the preparation in various products and to the products containing the preparation.
Gluten is a combination of proteins found in the endosperm of various grains, such as wheat, barley and rye, oats and other gluten-containing wheat variants, such as triticale, spelt and kamut. In wheat, gluten accounts for 90% of the protein and sakes up almost 15% of the total weight of a grain. It is thus an important source of protein.
However, gluten is the cause of a genetic disorder known as coeliac disease or gluten intolerance. Symptoms of coeliac disease can range from the classic features, such as diarrhea, weight loss, and malnutrition, to latent symptoms such as isolated nutrient deficiencies. The disease mostly affects people of European descent, and occurs more rarely in black and Asian populations. Those affected suffer damage to the villi (shortening and villous flattening) in the lamina propria and crypt regions of their intestines when they eat specific food-grain antigens (toxic amino acid sequences) that are found in wheat, rye, and barley, oats and other gluten-containing wheat variants, such as triticale, spelt and kamut. The gluten found in rice and corn do not cause the intolerance.
For persons with coeliac disease the toxic part of the gluten molecule is the prolamin portion: gliadin in wheat, secalin in rye and horedin in barley. Following a gluten-free diet, people can recover from the symptoms of the disease, but they cannot be cured. Re-introduction of gluten in the diet will again lead to symptoms.
Glutamine is an amino acid that occurs abundantly in gluten. Although it is not an essential amino acid it is nevertheless desirable for certain individuals, in particular those who are recovering from surgery, suffering from gastrointestinal disorders, immune function deficiencies, metabolic stress states, shock or performing endurance sports. Such individuals would benefit from supplementation with this amino acid, for example by taking a peptide preparation rich in glutamine.
Gluten is a very cost-effective source for such glutamine-rich peptide preparations. However, the known preparations are not suitable for coeliac patients since they still contain the toxic parts of the gliadin.
It is therefore the object of the present invention to provide a peptide preparation that is rich in bound glutamine but at the same time gluten free.
Such peptide preparation can be obtained by a method, comprising the steps of:
a) enzymatically hydrolysing gluten using one or more proteases to obtain a hydrolysate;
b) acidifying the hydrolysate to a pH between 4 and 5; and
c) filtering the hydrolysate to obtain the glutamine-rich gluten-free peptide preparation as the filtrate.
A glutamine-rich gluten-free is obtained by a method, comprising the steps of:
a) enzymatically hydrolysing gluten using one or more proteases to obtain a hydrolysate;
b) acidifying the hydrolysate to a pH between 4 and 5; and
c) filtering the hydrolysate to obtain the glutamine-rich gluten-free peptide preparation as the filtrate.
The term xe2x80x9cgluten-freexe2x80x9d is intended to indicate that the product when tested in an ELISA based on anti-xcexa9-gliadin antibodies yields a value of  less than 200 ppm. A suitable ELISA to test the gluten-free property is as described in the Association of Official Analytical Chemists"" (AOAC""s) Official Methods of Analysis, 15th Edition, 2nd supplement (1991),
It is clear that the proteases to be used can be selected from a wide range of proteases known in the art provided that hydrolysis performed with such protease results in a preparation that yields  less than 200 ppm in the above described ELISA. Proteases include acid, basic and neutral proteases derived from bacterial, fungal, animal or botanical sources. It was found that basic or neutral proteases active at a pH above 6 are particularly well suited. Examples of such proteases are Proleather N (Amano), Neutrase (NOVO), PROMOD 192P (Biocatalysts), Alcalase 2.4L (NOVO), Protease S (Amano), Peptidase A (Amano), Peptidase R (Amano). Of these the following proteases are preferred: Proleather N (Amano) and Alcalase 2.4L (NOVO).
The protein fragments that cause the hypersensitivity in coeliac patients are surprisingly removed when the hydrolysate is acidified and subsequently filtered. It is assumed that these fragments are precipitated and remain in the retentate of the filter. The pH to which the hydrolysate is to be acidified lies between 4 and 5, preferably between 4.1 and 4.9, more preferably between 4.3 and 4.8, most preferably between 4.5 and 4.7, and is optimally 4.6.
Hydrolysis is an essential step in the method of the invention as without hydrolysis the toxic fragments cannot be removed.
Peptide preparations that are obtainable by the method of the invention consisting of peptides that do not induce gluten hypersensitivity symptoms in coeliac patients are a further aspect of this invention. Such preparations are suitable as a food additive or food stuff for supplying additional glutamine to a subject. The preparation thus has sports and clinical applications and can be used in enteral nutrition and pet food.
The peptide preparation of the invention can be used in further products that can be taken by or administered to subjects in need of supplementation. Particular embodiments of such products are glutamine peptide tablets comprising the usual carriers, diluents and excipients for tablets and a peptide preparation of the invention as glutamine peptide source, glutamine peptide liquid beverage comprising the usual ingredients for beverages and a peptide preparation of the invention as glutamine peptide source, and glutamine peptide enteral nutrition comprising the usual carriers, diluents and excipients for enteral nutrition and a peptide preparation of the invention as glutamine peptide source.
Although the invention is more broadly applicable to gluten from all grains that may cause coeliac disease, it is preferred to use wheat because of its high glutamine content.
The present invention will be further elucidated in the following examples that are given for illustration purposes only and are in no way intended to limit the scope of the invention.